1) A y splitter is pretty much your only option for splitting the signal.
2) For splitting the remote turn on you can use a distribution block, relay or run the wire to the original amp and run another wire from the original amps turn on to the second amps turn on.
3) I think that setup would sound pretty nice. I would give each sub their own chamber though
4) I would do the Big 3 and get a battery
No one mentioned cat5 in this thread, although it works. Also, this does answer your question, your original question atleast because it wasn't specific.
You should have 12-16 square inches of port area per foot. Also, I would Make the port height 20.5 inches tall because it's easier but it height will work too
it won't defeat the purpose of having an eq. What the eq does is equalize sound (obviously). You will get the same frequencies with the two headunits, but the sound quality would be different
this is to back myself up about the 15 hrs a week..haha. I work at a daycare center that has an afterschool program to watch the elementary and intermediate schools in the district. The kids get there around 4 pm and the place closes at 7. I applied to watch afterschool so 3 hours times 5 days is 15 hours. The reason I don't work on weekends is because my parents are divorced and I go to my dads house on the weekends
I understand that the money will help, but to me it's not worth it. Of course I wouldn't get a crappy headunit with like .5 volt preouts. It all depends on what you are looking for. For example, my dad would do the upgrade because all he wants is SQ